Extensible and contractible wiring board and method for manufacturing extensible and contractible wiring board

ABSTRACT

An extensible and contractible wiring board that includes an extensible and contractible wiring sheet having an extensible and contractible resin sheet and an extensible and contractible wiring on the extensible and contractible resin sheet, the extensible and contractible wiring including a conductive particle, a resin, and a void at an interface between the conductive particle and the resin; and a fixing sheet on a main surface of the extensible and contractible wiring sheet.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International applicationNo. PCT/JP2019/022942, filed Jun. 10, 2019, which claims priority toJapanese Patent Application No. 2018-219247, filed Nov. 22, 2018, theentire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an extensible and contractible wiringboard and a method for manufacturing an extensible and contractiblewiring board.

BACKGROUND OF THE INVENTION

In recent years, a state of a human body and the like have been managedby acquiring and analyzing biological information.

For example, an extensible and contractible wiring board in which anextensible and contractible substrate is attached to a living body andused has been known as described in Patent Document 1.

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2016-145725

SUMMARY OF THE INVENTION

The extensible and contractible wiring board illustrated in PatentDocument 1 includes an extension and contraction sensing portioncontaining a conductive fiber and a resin binder. This portion extendsand contracts, and thus, electrical characteristics change. Accordingly,the extensible and contractible wiring board has been used as distortionsensor that senses distortion (extension and contraction).

However, in such an extensible and contractible wiring board, aphenomenon called a zero-drift in which a reference point of aresistance value changes whenever the expansion and contraction arerepeated is easy to occur, and there is a problem that a slope of achange in the resistance value change, which is an index of sensorsensitivity, is small.

The present invention has been made to solve the above problems, and anobject of the present invention is to provide an extensible andcontractible wiring board in which is hard to cause zero-drift and whichhas high sensitivity.

An extensible and contractible wiring board of the present inventionincludes an extensible and contractible wiring sheet having anextensible and contractible resin sheet and an extensible andcontractible wiring on the extensible and contractible resin sheet, theextensible and contractible wiring including a conductive particle, aresin, and a void at an interface between the conductive particle andthe resin; and a fixing sheet on a main surface of the extensible andcontractible wiring sheet.

A method for manufacturing an extensible and contractible wiring boardof the present invention includes: applying a first tensile stress to anextensible and contractible wiring sheet that includes an extensible andcontractible resin sheet and an extensible and contractible wiringformed on the extensible and contractible resin sheet; relaxing thefirst tensile stress; applying a second tensile stress to the extensibleand contractible wiring sheet after relaxing the first tensile stress;and securing a fixing sheet to a main surface of the extensible andcontractible wiring sheet in a state in which the second tensile stressis applied.

According to the present invention, it is possible to provide anextensible and contractible wiring board that is hard to causezero-drift and has high sensitivity.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a perspective view schematically illustrating an extensibleand contractible wiring board according to a first embodiment of thepresent invention.

FIG. 2 is an electron micrograph of an extensible and contractiblewiring in a state in which tensile stress is applied.

FIG. 3 is an electron micrograph of the extensible and contractiblewiring in a state in which the tensile stress is not applied.

FIG. 4 is a perspective view schematically illustrating an extensibleand contractible wiring board according to a second embodiment of thepresent invention.

FIG. 5 is a perspective view schematically illustrating an extensibleand contractible wiring board according to a third embodiment of thepresent invention.

FIG. 6(a) is a perspective view schematically illustrating an extensibleand contractible wiring sheet to which the tensile stress is notapplied, FIG. 6(b) is a perspective view schematically illustrating theextensible and contractible wiring sheet to which the tensile stress isapplied, and FIG. 6(c) is a perspective view schematically illustratinga state in which a state in which the tensile stress is applied to theextensible and contractible wiring is fixed by providing a fixing sheet.

FIG. 7(a) is a perspective view schematically illustrating a state inwhich an adhesive layer is provided on a main surface of the extensibleand contractible resin sheet on a side on which the extensible andcontractible wiring is not provided and a first fixing sheet is furtherprovided on the adhesive layer, FIG. 7(b) is a perspective viewschematically illustrating a state in which slits are formed in thefirst fixing sheet, FIG. 7(c) is a perspective view schematicallyillustrating a state in which the tensile stress is applied to theextensible and contractible wiring sheet and the first fixing sheet, andFIG. 7(d) is a perspective view schematically illustrating a state inwhich a state in which the tensile stress is applied to the extensibleand contractible wiring is fixed by providing a second fixing sheet onthe first fixing sheet.

FIG. 8(a) is a graph showing a relationship between strain, a resistancevalue, and a time in Example 1, and FIG. 8(b) is a graph showing arelationship between strain, a resistance value, and a time inComparative Example 1.

FIG. 9(a) is a graph showing the relationship between the strain and theresistance value in Example 1, and FIG. 9(b) is a graph showing therelationship between the strain and the resistance value in ComparativeExample 1.

FIG. 10(a) is a graph showing a relationship between strain and aresistance value of an extensible and contractible wiring sheet ofExample 2, and FIG. 10(b) is a relationship between strain and aresistance value of an extensible and contractible wiring sheet ofComparative Example 2.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an extensible and contractible wiring board of the presentinvention and a method for manufacturing an extensible and contractiblewiring board will be described.

However, the present invention is not limited to the followingconfigurations, and can be appropriately changed and applied withoutdeparting from the gist of the invention. Note that a combination of twoor more individual preferred configurations of the present invention tobe described below is also the present invention.

Needless to say, the embodiments to be illustrated below are examples,and partial configurations illustrated in different embodiments can bereplaced or combined. In second and subsequent embodiments, matterscommon to a first embodiment will not be described, and only differentpoints will be described. In particular, similar actions and effects dueto similar configurations will not be mentioned sequentially for eachembodiment.

In the following description, when the embodiments are not particularlydistinguished, the extensible and contractible wiring board of eachembodiment is simply referred to as the “extensible and contractiblewiring board of the present invention”.

First, the extensible and contractible wiring board of the presentinvention will be described.

First Embodiment

In the extensible and contractible wiring board of the presentinvention, an example in which a fixing sheet is provided on one mainsurface of an extensible and contractible wiring sheet will be describedas a first embodiment of the extensible and contractible wiring board ofthe present invention.

FIG. 1 is a perspective view schematically illustrating the extensibleand contractible wiring board according to the first embodiment of thepresent invention.

An extensible and contractible wiring board 1 illustrated in FIG. 1includes an extensible and contractible wiring sheet 30 that includes anextensible and contractible resin sheet 10 and an extensible andcontractible wiring 20 on the extensible and contractible resin sheet10.

The extensible and contractible wiring sheet 30 is a portion that isactually attached to a living body at the time of use and serves as aboard and a wiring that functions as a sensor.

Of a main surface 31 and a main surface 32 which are two main surfacesof the extensible and contractible wiring sheet 30, an adhesive layer 40is provided on the main surface 32 on a side on which the extensible andcontractible wiring 20 is not provided, and a fixing sheet 50 is furtherprovided on the adhesive layer 40.

The extensible and contractible resin sheet 10 is made of, for example,an extensible and contractible resin material. Examples of the resinmaterial include thermoplastic polyurethane and the like.

A thickness of the extensible and contractible resin sheet 10 is notparticularly limited, but is preferably 100 μm or less, and morepreferably 1 μm or less from the viewpoint of not inhibiting theexpansion and contraction of a front surface of the living body whenattached to the living body.

FIG. 1 illustrates a dumbbell type electrode in which electrodes 22 areprovided at both ends of a wiring 21 as an example of a shape of theextensible and contractible wiring 20. Shapes of the wiring and theelectrodes are not particularly limited, and can be arbitrarily changeddepending on a location and an application of use.

The extensible and contractible wiring 20 is fixed by the fixing sheet50 in a state in which tensile stress is applied in a directionindicated by a left right arrow L in FIG. 1 .

The extensible and contractible wiring has conductive particles and aresin as will be described later, and is a wiring having extensibilityand contractibility. For example, a mixture of a metal powder such asAg, Cu, or Ni as conductive particles and an elastomer-based resin suchas a silicone resin can be used.

An average particle size of the conductive particles is not particularlylimited, but is preferably 0.01 μm to 10 μm. A shape of the conductiveparticles is preferably spherical.

A thickness of the extensible and contractible wiring is notparticularly limited, but is preferably 1 μm to 100 μm, and morepreferably 1 μm to 50 μm.

The details of the extensible and contractible wiring in a state inwhich the tensile stress is applied will be described.

FIG. 2 is an electron micrograph of the extensible and contractiblewiring in a state in which the tensile stress is applied, and FIG. 3 isan electron micrograph of the extensible and contractible wiring in astate in which the tensile stress is not applied.

FIG. 2 illustrates conductive particles 23 and a resin 24 forming theextensible and contractible wiring 20, and further illustrates voids 25at an interface between the conductive particles 23 and the resin 24.

On the other hand, although there are the conductive particles 23 andthe resin 24 forming the extensible and contractible wiring 20 in FIG. 3, there are no voids at the interface between the conductive particles23 and the resin 24.

Thus, it can be seen that there are the voids in the extensible andcontractible wiring when the tensile stress is applied to the extensibleand contractible wiring. Since the voids are formed by the separation ofthe conductive particles, there are the voids at the interface betweenthe conductive particles and the resin.

In examples to be described later, effects of the extensible andcontractible wiring board in a state in which the tensile stress isapplied to the extensible and contractible wiring will be shown, butwhen the extensible and contractible wiring board is in a state in whichthe tensile stress is applied to the extensible and contractible wiring,there are the voids at the interface between the conductive particlesand the resin forming the extensible and contractible wiring. When thereare such voids in the extensible and contractible wiring, the extensibleand contractible wiring has a porous (sponge-lie) structure due to thepresence of the voids, and it is presumed that the elasticity of theextensible and contractible wiring increases. Zero-drift is hard tooccur due to the presence of such voids in the extensible andcontractible wiring, and thus, the sensitivity of the extensible andcontractible wiring board is improved.

As the state of the voids present in the extensible and contractiblewiring, it is preferable that fine voids are scattered throughout. It ispreferable that a size of the voids is substantially the same as a sizeof the conductive particles.

The strength of the tensile stress applied to the extensible andcontractible wiring in a state in which the extensible and contractiblewiring is fixed by the fixing sheet can be obtained by expressing, as anindex, ductility which is a length of the extensible and contractiblewiring with respect to a length of the extensible and contractiblewiring when the tensile stress is not applied. The ductility is notparticularly limited and may be determined by a material system of theextensible and contractible wiring, but is preferably 300% to 800%.

The length of the extensible and contractible wiring is a total lengthof the wiring 21 and the two electrodes 22 in FIG. 1 in the directionindicated by the left right arrow L.

Of the two main surfaces of the extensible and contractible wiring sheet30, the adhesive layer 40 is a layer provided on the main surface 32 onthe side on which the extensible and contractible wiring 20 is notprovided. The adhesive layer 40 is provided, and thus, the extensibleand contractible wiring sheet 30 of the extensible and contractiblewiring board 1 can be attached to a living body.

A material of the adhesive layer 40 is not particularly limited, andexamples thereof include adhesive resins such as acrylic polymers andurethane resins. A thickness of the adhesive layer 40 is notparticularly limited, but is preferably 0.1 μm to 10 μm, and morepreferably 0.1 μm to 1 μm.

The fixing sheet 50 is a sheet provided on the adhesive layer 40, and isa sheet for fixing the extensible and contractible wiring in a state inwhich the tensile stress is applied. Thus, the fixing sheet 50 needs tohave a strength so as not to be deformed due to tensile stress.

As the fixing sheet 50, a flexible film having low extensibility andcontractibility such as a PET film, a polystyrene film, a polypropylenefilm, or a polyimide film can be used.

The PET film is preferable since the PET film is hard, can be coped withroll-to-roll molding, and is inexpensive.

When the PET film is used as the fixing sheet 50, a thickness ispreferably 200 μm or more in order to have sufficient strength to fixthe extensible and contractible wiring.

Since the fixing sheet 50 is a sheet that is peeled off at the time ofuse of the extensible and contractible wiring board, it is preferablethat the fixing sheet is a sheet having good peel properties and havinggood release properties from the adhesive layer 40.

Second Embodiment

In the extensible and contractible wiring board of the presentinvention, an example in which the fixing sheets are provided on boththe main surfaces of the extensible and contractible wiring sheet willbe described as a second embodiment of the extensible and contractiblewiring board of the present invention.

FIG. 4 is a perspective view schematically illustrating the extensibleand contractible wiring board according to the second embodiment of thepresent invention.

An extensible and contractible wiring board 2 illustrated in FIG. 4 hasa configuration in which a fixing sheet is also provided on the mainsurface 31 (main surface on a side on which the extensible andcontractible wiring 20 is provided) of the extensible and contractiblewiring sheet 30 in the extensible and contractible wiring board 1illustrated in FIG. 1 .

The fixing sheet provided on the main surface 31 of the extensible andcontractible wiring sheet 30 is a fixing sheet 51 and the fixing sheetprovided on the main surface 32 is a fixing sheet 52.

The fixing sheet 51 and the fixing sheet 52 may be the same fixing sheetor different fixing sheets.

The adhesive layer is not provided between the main surface 31 of theextensible and contractible wiring sheet 30 and the fixing sheet 51.

The fixing sheets are preferably provided on both the main surfaces ofthe extensible and contractible wiring sheet in the extensible andcontractible wiring board from the viewpoint of work efficiency when theextensible and contractible wiring sheet is attached to the living body.

When the extensible and contractible wiring board 2 illustrated in FIG.4 is used, the fixing sheet 52 is peeled off immediately beforeattaching to the living body, and the adhesive layer 40 is exposed. Themain surface 32 side of the extensible and contractible wiring sheet 30is attached to the living body by an adhesive force of the adhesivelayer 40. At this point, a state in which the tensile stress is appliedto the extensible and contractible wiring 20 is maintained by the fixingsheet 51. The fixing sheet 51 is peeled off after the extensible andcontractible wiring sheet is attached to the living body, and thus, itis possible to complete the attachment of the extensible andcontractible wiring sheet 30 in a state in which the tensile stress isapplied to the extensible and contractible wiring 20.

Third Embodiment

In the extensible and contractible wiring board of the presentinvention, an example in which the fixing sheets provided on the mainsurface of the extensible and contractible resin sheet on the side onwhich the extensible and contractible wiring is not provided include afirst fixing sheet having slits and a second fixing sheet on the firstfixing sheet will be described as a third embodiment of the presentinvention.

FIG. 5 is a perspective view schematically illustrating the extensibleand contractible wiring board according to the third embodiment of thepresent invention.

An extensible and contractible wiring board 3 illustrated in FIG. 5 isdifferent from the extensible and contractible wiring board 2illustrated in FIG. 4 in a configuration of the fixing sheet on the mainsurface 32 (main surface on the side on which the extensible andcontractible wiring is not provided) side of the extensible andcontractible wiring sheet 30.

The extensible and contractible wiring board 3 illustrated in FIG. 5 isillustrated upside down from the extensible and contractible wiringboard 2 illustrated in FIG. 4 , and the main surface 32 side of theextensible and contractible wiring sheet 30 faces up and the mainsurface 31 side faces down.

The fixing sheets on the main surface 32 side of the extensible andcontractible wiring sheet 30 include a first fixing sheet 53 provided onthe adhesive layer 40 and a second fixing sheet 54 provided on a firstfixing sheet 53.

The first fixing sheet 53 has slits 55 in a direction transverse to adirection of the tensile stress applied to the extensible andcontractible wiring 20 (direction indicated by a left right arrow L inFIG. 5 ).

The fact that the direction of the slits is transverse with respect tothe direction of the tensile stress applied to the extensible andcontractible wiring means that the direction of the tensile stress andthe direction of the slits are not parallel.

An angle formed by the direction of the tensile stress applied to theextensible and contractible wiring and the direction of the slits ispreferably 90°.

Such an extensible and contractible wiring board is suitable for fixingthe extensible and contractible wiring with the fixing sheets in a statein which the tensile stress is applied in a manufacturing step.

The fixing sheets are preferably provided on both the main surfaces ofthe extensible and contractible wiring sheet from the viewpoint of workefficiency when the extensible and contractible wiring sheet is attachedto the living body as described for the extensible and contractiblewiring board of the second embodiment.

The extensible and contractible wiring board of the present inventioncan be used as a sensor for acquiring and analyzing biologicalinformation by attaching the extensible and contractible wiring sheet tothe living body in a state in which the tensile stress is applied to theextensible and contractible wiring. The extensible and contractiblewiring in a state in which the tensile stress is applied includes theconductive particles, the resin, and the voids present at the interfacebetween the conductive particles and the resin. The sensor includingsuch extensible and contractible wiring is hard to cause zero-drift. Thesensitivity of the sensor is improved.

Hereinafter, the method for manufacturing the extensible andcontractible wiring board of the present invention will be described.

FIG. 6(a) is a perspective view schematically illustrating theextensible and contractible wiring sheet to which the tensile stress isnot applied, FIG. 6(b) is a perspective view schematically illustratingthe extensible and contractible wiring sheet to which the tensile stressis applied, and FIG. 6(c) is a perspective view schematicallyillustrating a state in which the tensile stress is applied to theextensible and contractible wiring and is fixed by providing the fixingsheets.

(Extensible and Contractible Wiring Sheet Preparation Step)

The extensible and contractible wiring sheet including the extensibleand contractible resin sheet and the extensible and contractible wiringformed on the extensible and contractible resin sheet is prepared.

FIG. 6(a) illustrates the extensible and contractible wiring sheet 30 towhich the tensile stress is not applied. The adhesive layer 40 isprovided on one main surface 32 of the extensible and contractiblewiring sheet 30, but the adhesive layer may or may not be provided atthis stage.

(First Extension Step)

In a first extension step, the tensile stress is applied to theextensible and contractible wiring sheet.

FIG. 6(b) illustrates a state in which the tensile stress is applied tothe extensible and contractible wiring sheet 30 illustrated in FIG. 6(a)in a direction indicated by a left right arrow L.

By this first extension step, the voids are formed at the interfacebetween the conductive particles and the resin forming the extensibleand contractible wiring.

(Relaxation Step)

In a relaxation step, the tensile stress applied in the first extensionstep is relaxed. The state illustrated in the drawing is the same as thestate of the extensible and contractible wiring sheet 30 to which thetensile stress is not applied as illustrated in FIG. 6(a).

(Second Extension Step)

In a second extension step, the tensile stress is applied to theextensible and contractible wiring sheet again.

The state illustrated in the drawing is the same as the state of theextensible and contractible wiring sheet 30 to which the tensile stressis applied as illustrated in FIG. 6(b).

(Fixing Step)

In a fixing step, the fixing sheets are provided on the main surfaces ofthe extensible and contractible wiring sheet in a state in which thetensile stress applied in the second extension step is applied to theextensible and contractible wiring.

FIG. 6(c) illustrates a state in which the fixing sheet 51 is providedon the main surface 31 of the extensible and contractible wiring sheet30 and the fixing sheet 52 is provided on the main surface 32 with theadhesive layer 40 interposed therebetween.

The fixing sheet 51 and the fixing sheet 52 are provided, and thus, astate in which the tensile stress applied in the second extension stepis applied to the extensible and contractible wiring 20 is fixed.

A thin adhesive layer (not illustrated) is provided at the fixing sheet51, and the fixing sheet 51 is fixed to the main surface 31 of theextensible and contractible wiring sheet 30. Since this adhesive layerstrongly adheres to the fixing sheet 51 side and remains on the fixingsheet 51 side when the fixing sheet 51 is peeled off at the time of useof the extensible and contractible wiring board, this adhesive layerdoes not remain on a front surface of the extensible and contractiblewiring sheet 30.

The extensible and contractible wiring board obtained in this manner isthe same as the extensible and contractible wiring board 2 illustratedin FIG. 4 .

FIG. 6(c) illustrates a form in which the fixing sheets are provided onboth the main surface 31 and the main surface 32 of the extensible andcontractible wiring sheet 30, but the fixing sheet may be provided onlyon one of the main surfaces.

In the above steps, a tension rate and ductility in the first extensionstep and the second extension step are not particularly limited, and canbe changed depending on the material system of the extensible andcontractible wiring.

Next, another embodiment of the method for manufacturing the extensibleand contractible wiring board of the present invention will bedescribed.

In this embodiment, the extensible and contractible wiring board 3illustrated in FIG. 5 in which the fixing sheets provided on the mainsurface of the extensible and contractible resin sheet on the side onwhich the extensible and contractible wiring is not provided include thefirst fixing sheet having the slits and the second fixing sheet providedon the first fixing sheet is manufactured.

FIG. 7(a) is a perspective view schematically illustrating a state inwhich the adhesive layer is provided on the main surface of theextensible and contractible resin sheet on the side on which theextensible and contractible wiring is not provided and the first fixingsheet is further provided on the adhesive layer, FIG. 7(b) is aperspective view schematically illustrating a state in which the slitsare formed in the first fixing sheet, FIG. 7(c) is a perspective viewschematically illustrating a state in which the tensile stress isapplied to the extensible and contractible wiring sheet and the firstfixing sheet, and FIG. 7(d) is a perspective view schematicallyillustrating a state in which a state in which the tensile stress isapplied to the extensible and contractible wiring is fixed by providingthe second fixing sheet on the first fixing sheet.

(First Fixing Sheet Forming Step)

In a first fixing sheet forming step, after the extensible andcontractible wiring sheet preparation step, the adhesive layer isprovided on the main surface of the extensible and contractible resinsheet on the side on which the extensible and contractible wiring is notprovided and the first fixing sheet is further provided on the adhesivelayer.

In FIG. 7(a), a state in which the adhesive layer 40 is provided on onemain surface 31 of the extensible and contractible wiring sheet 30 onthe side on which the extensible and contractible wiring is not providedand the first fixing sheet 53 is further provided on the adhesive layer40 illustrated. The tensile stress is not applied at this point.

(Slit Forming Step)

In a slit forming step, the slits are formed in the first fixing sheetin a direction transverse with respect to a direction of predeterminedtensile stress applied to the extensible and contractible wiring sheet.

FIG. 7(b) illustrates a state in which the slits 55 are formed in thefirst fixing sheet 53.

Since the direction of the predetermined tensile stress applied to theextensible and contractible wiring sheet is the direction indicated bythe left right arrow L in FIG. 7(b), the slits are formed in thedirection inclined (direction is not parallel) with respect to thisdirection. The slits are formed in the first fixing sheet, and thus, thefirst fixing sheet can also be extended together in the subsequent firstextension step.

(First Extension Step)

In the first extension step, the tensile stress is applied to theextensible and contractible wiring sheet and the first fixing sheet.

FIG. 7(c) illustrates a state in which the tensile stress is applied tothe extensible and contractible wiring sheet 30 and the first fixingsheet 53.

Since the slits 55 are provided in the first fixing sheet 53, the firstfixing sheet 53 can be extended together with the extensible andcontractible wiring sheet 30.

The first fixing sheet 53 is provided, and thus, the first extensionstep can be performed while maintaining a state in which the adhesivelayer 40 is not exposed. Accordingly, the work efficiency is excellent.

By this first extension step, the voids are formed at the interfacebetween the conductive particles and the resin forming the extensibleand contractible wiring.

(Relaxation Step)

In a relaxation step, the tensile stress applied in the first extensionstep is relaxed. The state illustrated in the drawing is the same as thestate of the extensible and contractible wiring sheet 30 and the firstfixing sheet 53 to which the tensile stress is not applied asillustrated in FIG. 7(b).

(Second Extension Step)

In a second extension step, the tensile stress is applied to theextensible and contractible wiring sheet again.

The state illustrated in the drawing is the same as the state of theextensible and contractible wiring sheet 30 and the first fixing sheet53 to which the tensile stress is applied as illustrated in FIG. 7(c).

(Fixing Step)

In the fixing step, a state in which the tensile stress is applied tothe extensible and contractible wiring is fixed by providing the secondfixing sheet on the first fixing sheet.

FIG. 7(d) illustrates a state in which the tensile stress is applied tothe extensible and contractible wiring 20 is fixed by providing thesecond fixing sheet 54 on the first fixing sheet 53. The fixing sheet 51is also provided on the main surface 31 of the extensible andcontractible wiring sheet 30.

The second fixing sheet 54 and the fixing sheet 51 are provided, andthus, a state in which the tensile stress applied in the secondextension step is applied to the extensible and contractible wiring 20is fixed.

A thin adhesive layer (not illustrated) is provided at the fixing sheet51, and the fixing sheet 51 is fixed to the main surface 31 of theextensible and contractible wiring sheet 30. Since this adhesive layerstrongly adheres to the fixing sheet 51 side and remains on the fixingsheet 51 side when the fixing sheet 51 is peeled off at the time of useof the extensible and contractible wiring board, this adhesive layerdoes not remain on a front surface of the extensible and contractiblewiring sheet 30.

A thin adhesive layer (not illustrated) is also provided at the secondfixing sheet 54, and the second fixing sheet 54 is fixed to the firstfixing sheet 53. The fixing between the second fixing sheet 54 and thefirst fixing sheet 53 may be firmly performed. Since the second fixingsheet 54 and the first fixing sheet 53 are peeled off at once at thetime of use of the extensible and contractible wiring board, it ispreferable that the second fixing sheet 54 and the first fixing sheet 53are not peeled off.

The extensible and contractible wiring board obtained in this manner isthe same as the extensible and contractible wiring board 3 illustratedin FIG. 5 .

Although FIG. 7(d) illustrates a form in which the fixing sheet 51 isprovided on the main surface 31 of the extensible and contractiblewiring sheet 30, the fixing sheet 51 may not be provided.

Examples

Hereinafter, examples in which the extensible and contractible wiringboard of the present invention is disclosed more specifically will beillustrated. The present invention is not limited to these examples.

An extensible and contractible wiring sheet was prepared by forming adumbbell type wiring made of a mixture of a metal powder and anelastomer resin in a thermoplastic polyurethane resin as an extensibleand contractible resin sheet.

A relationship between strain applied to the extensible and contractiblewiring sheet and a resistance value was measured in Example 1 in whichthe extension step of applying the tensile stress is performed on thisextensible and contractible wiring sheet and Comparative Example 1 inwhich the extension step of applying the tensile stress is notperformed. The measurement was performed immediately after the extensionstep.

FIG. 8(a) is a graph showing a relationship between the strain, theresistance value, and a time in Example 1, and FIG. 8(b) is a graphshowing a relationship between the strain, the resistance value, and atime in Comparative Example 1.

In this test, a change in the resistance value for the strain wasmeasured by repeatedly applying the strain about 3 times in 50 secondsbetween 0% and −20%.

From this result, it can be seen that the resistance value when thestrain is 0% does not change even after the strain is repeatedly appliedin Example 1. On the other hand, it can be seen that the resistancevalue when the strain is 0% increases as the strain is repeatedlyapplied in Comparative Example 1. That is, zero-drift does not occur inExample 1, and zero-drift occurs in Comparative Example 1.

FIG. 9(a) is a graph showing the relationship between the strain and theresistance value in Example 1, and FIG. 9(b) is a graph showing therelationship between the strain and the resistance value in ComparativeExample 1.

In this test, the change in the resistance value for the strain wasmeasured while gradually increasing the strain between 0% and −20%. Aplurality of lines shows a plurality of results when the test isrepeatedly performed.

In Example 1, the resistance value for the strain of 0% is about 7 to9Ω, and the resistance value for the strain of 20% is about 22 to 25Ω.On the other hand, in Comparative Example 1, the resistance value forthe strain of 0% is about 0.8 to 1.4Ω, and the resistance value for thestrain of 20% is about 1.5 to 2.0Ω.

Since the amount of change in the resistance differs by about 10 times,it can be seen that Example 1 can be used as a sensor with highersensitivity. The change in the resistance value for the strain is linearin Example 1, but is not linear and has a slightly S-shaped curve inComparative Example 1.

Thus, it can be seen that the relationship between the strain and theresistance value is clearer in Example 1 and the performance as a sensorfor measuring the strain by the change in the resistance value is high.

Next, test results for confirming an effect of maintaining a state inwhich the tensile stress is applied to the extensible and contractiblewiring after the extension step are shown. Similar to Example 1, Example2 in which an extensible and contractible wiring sheet obtained byperforming the first extension step of applying the tensile stress tothe extensible and contractible wiring sheet, performing the secondextension step after the relaxation step was performed, and fixing astate in which the tensile stress was applied to the extensible andcontractible wiring by the fixing sheet was stored for one day wasprepared. Similar to Example 1, Comparative Example 2 in which anextensible and contractible wiring sheet obtained by performing therelaxation step after the first extension step of applying the tensilestress to the extensible and contractible wiring sheet, not performingthe second extension step, and further not performing the fixing withthe fixing sheet was stored for one day was prepared.

A relationship between strain applied to the extensible and contractiblewiring sheet and a resistance value was measured for the extensible andcontractible wiring sheets of Example 2 and Comparative Example 2. Theextensible and contractible wiring sheet of Example 2 was measuredimmediately after the fixing sheet was peeled off.

FIG. 10(a) is a graph showing the relationship between the strain andthe resistance value of the extensible and contractible wiring sheet ofExample 2, and FIG. 10(b) is the relationship between the strain and theresistance value of the extensible and contractible wiring sheet ofComparative Example 2.

When FIG. 10(a) and FIG. 10(b) are compared, the extensible andcontractible wiring sheet of Example 2 has high linearity of a change inthe resistance value for the strain and small variation. The amount ofchange in the resistance value is also large, and thus, it can be seenthat the extensible and contractible wiring sheet of Example 2 can beused as a sensor with high sensitivity.

The extensible and contractible wiring sheet of Comparative Example 2has low linearity of a change in the resistance value for the strain andhas large variation. The amount of change in the resistance value issmall, and thus, it can be seen that the sensitivity as the sensor islow.

DESCRIPTION OF REFERENCE SYMBOLS

-   1, 2, 3: Extensible and contractible wiring board-   10: Extensible and contractible resin sheet-   20: Extensible and contractible wiring-   21: Wiring-   22: Electrode-   23: Conductive particles-   24: resin-   25: Void-   30: Extensible and contractible wiring sheet-   31: Main surface of extensible and contractible wiring sheet (main    surface on extensible and contractible wiring side)-   32: Main surface of extensible and contractible wiring sheet (main    surface not on extensible and contractible wiring side)-   40: Adhesive layer-   50, 51, 52: Fixing sheet-   53: First fixing sheet-   54: Second fixing sheet-   55: Slit

The invention claimed is:
 1. An extensible and contractible wiring boardcomprising: an extensible and contractible wiring sheet that includes anextensible and contractible resin sheet and an extensible andcontractible wiring on the extensible and contractible resin sheet, theextensible and contractible wiring including a conductive particle, aresin, and a void at an interface between the conductive particle andthe resin; a first fixing sheet on a first main surface of theextensible and contractible wiring sheet opposite to a second mainsurface of the extensible and contractible wiring sheet having theextensible and contractible wiring; a second fixing sheet on the secondmain surface; and an adhesive layer between the first main surface ofthe extensible and contractible wiring sheet and the first fixing sheet,wherein the extensible and contractible wiring is in a state in whichtensile stress is applied thereto, wherein the first fixing sheet has aslit in a direction transverse with a direction of the tensile stressapplied to the extensible and contractible wiring, and the extensibleand contractible wiring board further comprises: a third fixing sheet onthe first fixing sheet.
 2. An extensible and contractible wiring boardcomprising: an extensible and contractible wiring sheet that includes anextensible and contractible resin sheet and an extensible andcontractible wiring on the extensible and contractible resin sheet, theextensible and contractible wiring including a conductive particle, aresin, and a void at an interface between the conductive particle andthe resin; a first fixing sheet on a first main surface of theextensible and contractible wiring sheet opposite to a second mainsurface of the extensible and contractible wiring sheet having theextensible and contractible wiring; a second fixing sheet on the secondmain surface; and an adhesive layer between the first main surface ofthe extensible and contractible wiring sheet and the first fixing sheet,wherein the first fixing sheet has a slit in a direction transverse witha direction of the tensile stress applied to the extensible andcontractible wiring, and the extensible and contractible wiring boardfurther comprises: a third fixing sheet on the first fixing sheet.
 3. Anextensible and contractible wiring board comprising: an extensible andcontractible wiring sheet that includes an extensible and contractibleresin sheet and an extensible and contractible wiring on the extensibleand contractible resin sheet, the extensible and contractible wiringincluding a conductive particle, a resin, and a void at an interfacebetween the conductive particle and the resin; a first fixing sheet on afirst main surface of the extensible and contractible wiring sheetopposite to a second main surface of the extensible and contractiblewiring sheet having the extensible and contractible wiring; and anadhesive layer between the first main surface of the extensible andcontractible wiring sheet and the first fixing sheet, wherein the firstfixing sheet has a slit in a direction transverse with a direction ofthe tensile stress applied to the extensible and contractible wiring,and the extensible and contractible wiring board further comprises: asecond fixing sheet on the first fixing sheet.